POST a QUESTION or READ FAQs about methods used in testing structural wood members for damage or decay & the role of micro-drilling tests for in-situ evaluation of structural wood beams, timbers, or other framing members in buildings..

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Using thermal imaging (thermography) for determining the soundness of wood structural members:

Really? This article discusses the role of thermal imaging in assessing the condition of wood structural members such as beams, timbers, joists, rafters, posts.

This article series surveys methods used to test & evaluate the structural integrity of wood-framed buildings where focus is on the condition of structural wood posts, beams and other framing members. We discuss the problems surrounding hidden rot or decay, the presence or absence of moisture or other instrument-detectable clues, and the problem of subjective decisions to replace or not-replace suspect wood structural members.

Are Thermal Images Reliable for Spotting Areas of Extra Risk of Structural Rot Damage or Hidden Mold in Buildings?

This article series is adapted & expanded from the author's "An Introduction to Micro-Drilling Technology for N. Z. Structural Timber Assessment" and is used with permission. We [DF] have added comments, some illustrations, and additional article citations.

At the references section we include a link to the original article as well as contact information for the authors and Incodo Ltd., a Tauranga, New Zealand forensic engineering firm.

[Click to enlarge any image or illustration]

OPINION: DF: Thermal images and IR have been widely used with some success at spotting areas of heat loss in buildings and these tools have a longer history of use in examining overheated electrical connections, motors, etc. But for finding hidden mold, moisture, rot, or structural damage, thermography is a risky proposition.

Thermography, based on observing temperature differences, reports just that: temperature differences. In some but not all circumstances, a temperature variation in a building may relate to a leak or moisture presence that in turn might indicate an area where there is risk of rot. But what if an old leak caused rot damage but has now dried out? In short, as with any study, absence of evidence is not evidence of absence of a problem.

Watch out: in the hands of the un-trained or unscrupulous these and other tools can wreak havoc or harm to consumers. The most egregious instrument snafu I've come across [DF] recently was a Hudson Valley New York "mold remediator" uses an IR camera to tell his clients where the hidden mold is located in their home - it was a modern version of the guy with the light meter who sold people replacement windows by showing clients where their heat loss was occurring - wherever there was light.

I did find areas of basement water entry and moldy insulation - in an area not addressed by the New York mold-thermographer. Details about using thermal imaging to look for hidden mold are
at THERMAL IMAGING MOLD SCANS.

Paul Probett adds: We had major problems with people buying thermal imagers, using ex military units and making ridiculous claims. In 2008 I gave a power-point presentation [25] to a conference explaining how IR results can be fudged and I described the limitations of thermal imagers. (Our staff had been through the Infraspection Institute USA on-line course to level 2 the year before).

Mr. Probett's power point presentation on using thermography in building damage or mold surveys is adapted and expanded
at THERMAL IMAGING, THERMOGRAPHY

Note: Above information is copyright, commercially sensitive and is yet to be peer reviewed. It is not to be copied or circulated without the express and written permission of Incodo Limited. Adapted here by InspectaPedia.com, with permission from Incodo 8/5/2012, technical review is in process.

V4a 06/12 - ####

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The Forensic Building Pathology division provides evidence in report form to government agencies, consultancy firms, lawyers and others, when truly independent analysis based on comprehensive testing is required. Incodo arguably has the largest, most up-to-date and comprehensive range of building investigation equipment available and has developed unique methodologies particularly in the field of non-destructive testing for leaking structures.

This technology is objective and evidential in nature and provides assessment as to whether wood is significantly decayed, suspect or suitable for retention. The technology has particular application in locating and assessing hidden decay.

[2] Thomas Tannert, Andreas Muller, Mareike Vogel, "Applications and limitations of NDT: a timber bridge case study", NDTCE’09, Non-Destructive Testing in Civil Engineering
Nantes, France, June 30th – July 3rd, 2009, web search 8/3/2012, original source: http://www.ndt.net/article/ndtce2009/papers/144.pdf [copy on file as Tannert_Timber_Test_144.pdf]AbstractThe applications and limitations of different non-destructive and semi-destructive
techniques to evaluate the structural integrity of timber members in a pedestrian bridge are
presented as a case study. Sophisticated assessment tools are required to detect hidden
damages in timber structures: for example stress-wave techniques are used to evaluate the
modulus of elasticity of bending members and resistance to drilling is used to gain knowledge
of areas of changed density due to insect or moisture induced damages. Reliably relating the
gathered data to the structural integrity of the structure is a complex issue. Bending members
and connection details of a decommissioned timber bridge were evaluated using non
destructive assessment tools. Eventually these parts were tested destructively to assess their
remaining modulus of elasticity and load bearing capacity. The need for improvements in the
current practice is highlighted by comparing the results from the non-destructive, semidestructive
and destructive tests.

[3] Bohumil Kasal, Thomas Tannert, "RILEM Technical Committee on In Situ Assessment of Structural Timber", Bohumil Kasal et al., 2010, Advanced Materials Research, 133-134, 271, Abstract:
Timber is an intriguing structural material and the only one that is truly renewable. Being biodegradable, hygroscopic and non-isotropic, it presents special challenges when assessing its integrity in structures. The presented paper outlines the major issues related to in-situ evaluation of structural timber and summarizes the work of the RILEM Technical Committee 215-AST “In-situ assessment of structural timber”. The committee was established in 2005 to bring together leading scientists and practitioners in the field of evaluation of timber in existing structures. Timber structures have been investigated for decades using numerous techniques that have been either developed specifically for the material or were transferred from other fields of investigation. A state-of-the-art report describing existing and emerging technologies and methods was prepared by the RILEM committee. The report describes the principles, the applications and the limitations of major evaluation techniques for in-situ assessment of timber. A brief discussion of codes standards and future research needs shows that much needs to be done in this area. As a present activity, harmonized test procedure recommendations are being prepared that will provide the engineering community with valuable guidance when evaluating timber structures.

[5] Bohumil Kasal, Tension Micro Specimens,
In Situ Assessment of Structural Timber
RILEM State of the Art Reports, 2011, Volume 7, 75-80, DOI: 10.1007/978-94-007-0560-9_8, [excepts chapter 7 on file: Tension Micro-Specimens, as Kasal_Testing.pdf]
Abstract
The principle of this method is extracting triangular specimens (about 5 mm equal-sides triangle) along the length of the member. Small-kerf circular saw with a fixture attached to the surface of the member is used to extract the specimens. Specimens are then glued to the test blocks and tested in tension. The method gives direct values of tensile modulus of elasticity and strength for clear wood. The values are local and pertain to the tested area and surface.
[From chapter 7.1 Background: This method was developed by Kasal and is based on direct measurement of tension properties along fibers. Bending strength evaluation is an important aspect of in situ evaluation of timber members as it is one of the predominant modes of loading, but estimates of the bending properties in situ can present a challenge. With information on the member's tensile properties, bending strength estimates can be made; tensile strength has been related to bending strength and is considered to be approximately equal. Tensile properties have a poor correlation with compression properties therefore tensile strength can not be estimated using information attained with the core drilling technique. Specimens can however be extracted to evaluate the tensile properties of in situ members with the technique described in the following sections....']

[6] Thomas Tannert, Andreas Müller, Mareike Vogel, "in-situ assessment, hot spots, moisture content, block-laminated timber", ICTB 2010, Bern University of Applied Sciences. ISBN 978 8251 926805, in-situ assessment, hot spots, moisture content, block laminated timber,
Abstract:Timber has been a structural material for bridges for centuries and numerous examples throughout the world demonstrate its durability. But timber is biodegradable and hygroscopic and regular inspections are recommended to determine the condition of the structure. This paper reports on the structural health monitoring of timber bridges in general and the long term moisture measurement inside block-laminated timber elements of several traffic bridges in specific. Presently there is no reported scientific information available on the long-term moisture behaviour and the resulting moisture induced stresses and dimensional changes of block-laminated timber elements. The paper reports on the monitoring of the moisture content of a block-laminated timber bridge.[References 7-13 below are cited from this document]

[16] Bob Monk, "Evaluation of Decay Detection Equipment in Standing Trees", USDA Forest Service, web search 8/4/12, original source http://www.fs.fed.us/eng/techdev/IM/tree_decay/tree_decay_detect_equip.shtml [Copy on file as Monk_Tree_Deday_Detection.pdf] Introduction - quoting:A project was proposed to test and compare several of the devices that are able, to some
degree, to detect decay in trees. Decay in trees is directly related to the hazards that they
present. However, detection of decay does not necessarily mean that a tree is hazardous. The
identified devices can be used to determine what decay is present. It is still necessary to use
professional experience and sound judgment to decide if a tree actually poses a hazard.
General guides or "rules of thumb" can also be used, such as Guidance notes from the
Minnesota Department of Natural Resources and the USDA Forest Service, 1996 that suggests
a 25 mm ring of sound wood is required for every 150 mm of stem diameter at any point on
the stem. If the proportion of decayed wood to sound wood exceeds this level then action may
need to be taken to minimize the hazard posed by the tree (Lawday and Hodges, 2000). [Additional selected citations from this article are below]

[16b] Moore, W. 1999. The Combined Use of the Resistograph and the Shigometer for the Accurate
Mapping and Diagnosis of the Internal Condition of woody Support Organs of Trees.
Arboriculture Journal. 23: 273-287

[18] Pilodyn Wood Tester, Hylec Controls, available in Australia from Ferret http://www.ferret.com.au/n/Pilodyn-wood-density-meter-from-Hylec-n852069 - Quoting:Pilodyn, available from Hylec Controls , was developed to determine the density and strength of dead and living wood. Invisible soft rot can be detected rapidly and objectively in an easy non-destructiveway and the reduction in strength associated with it can be determined. This can be of vital importance in the case of wooden playground structures,climbing frames and telephone masts.
With PILODYN 6J Forestversion the density of the wood is determined on living trees. The damage is so little that the tree suffers no harm and the testing method is regarded as non-destructive.
Testing procedure: The testing procedure is very simple: The tester is loaded with the ramrod and then pressed firmly onto the tet surface. The impact pin is shot into the wood by pressing the trigger cover. The depth of penetrationcan be read straightaway in mm on the scale mounted on the tester.
Typical applications of the Pilodon:
Testing the stability of wooden structures on playgrounds, detection of soft rot
Testing the strength on wooden telephone masts, detection of soft rot
When thinning out: sorting out trees with undesirable density of the wood
Early detection of diseases: periodic measurement detects unnatural changes in the wood density
Comparison of the location-dependent density to determine the optimal location for the respective tree species
Establishing productivity with respect to density for the same tree species and similar location properties for culture purposes
Testing and sorting of cut wood into timber classes

[20] Brashaw, Brian K.; Vatalaro, Robert J.; Wacker, James P.; Ross, Robert J. 2005. "Condition Assessment of Timber Bridges: 1. Evaluation of a Micro-Drilling Resistance Tool" Gen. Tech. Rep. FPL-GTR-159. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 8 p., web search 8/5/2012, original source: http://www.fpl.fs.fed.us/documnts/fplgtr/fpl_gtr159.pdf [copy on file as Micro_Drill_Study_USDA_fpl_gtr159.pdf] This publication is also available from the U.S. FPL at www.fpl.fs.fed.us
Abstract:The research presented in this report was conducted to evaluate the accuracy and reliability of a commercially available micro-drilling resistance device, the IML RESI F300-S (Instrument Mechanic Labor, Inc., Kennesaw, Georgia), in locating deteriorated areas in timber bridge members. The device records drilling resistance as a function of drilling depth, which allows the operator to assess the location of deterioration in the member cross section. Bridge components containing different levels of natural decay were used as test specimens in this study. The IML RESI F300-S was first used to assess decay in the timber bridge specimens. The specimens were then sawn along their length into slabs to expose their interior condition. The interior faces of these slabs were inspected visually and with a stress-wave probe to confirm if deterioration was present. On the basis of these tests, we conclude that this micro-drilling device accurately determines if deterioration is present at the point at which the test is performed.
Keywords: timber, bridges, inspection, drilling resistance, nondestructive evaluation
Excerpt from the study's conclusions:Based on our tests, we offer the following comments about the accuracy of using the IML RESI F300-S for locating deterioration in bridge timbers:
1. The tool is accurate at determining the presence of decay in timber bridge specimens. However, these data are limited to the drilling location.
2. The tool can precisely locate an internal defect (decay pocket, check, or split) within the member’s cross section. This can be advantageous for condition assessment and load rating purposes.
3. Decay indices were developed for Douglas-fir timbers
as follows: sound, >25% resistance; moderate decay, 10–25%; and advanced or severe decay, 0–10%.
One drawback is that multiple, time-consuming drilling would be required to map the area and extent of the decay in the other plane. Another possible drawback is the potential to spread the decay to sound areas within a timber or to sound timbers by multiple use of a contaminated drill bit. Routine cleaning of drill bits, or replacement with a new one, would greatly reduce this potential drawback.
It is crucial to use this or any nondestructive testing tool or device as part of a comprehensive condition assessment. Such an assessment should incorporate an in-depth visual inspection, knowledge of prior use of the structure, and a working knowledge of fundamental engineering properties of structural wood products. This technique, when used in concert with visual and ultrasound techniques, would provide a very accurate description of the condition of timbers.

Steve Bliss's Building Advisor at buildingadvisor.com helps homeowners & contractors plan & complete successful building & remodeling projects: buying land, site work, building design, cost estimating, materials & components, & project management through complete construction. Email: info@buildingadvisor.com
Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education.
Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com

Design of Wood Structures - ASD, Donald E. Breyer, Kenneth Fridley, Kelly Cobeen, David Pollock, McGraw Hill, 2003, ISBN-10: 0071379320, ISBN-13: 978-0071379328
This book is an update of a long-established text dating from at least 1988 (DJF); Quoting:This book is gives a good grasp of seismic design for wood structures. Many of the examples especially near the end are good practice for the California PE Special Seismic Exam design questions. It gives a good grasp of how seismic forces move through a building and how to calculate those forces at various locations.THE CLASSIC TEXT ON WOOD DESIGN UPDATED TO INCLUDE THE LATEST CODES AND DATA. Reflects the most recent provisions of the 2003 International Building Code and 2001 National Design Specification for Wood Construction. Continuing the sterling standard set by earlier editions, this indispensable reference clearly explains the best wood design techniques for the safe handling of gravity and lateral loads. Carefully revised and updated to include the new 2003 International Building Code, ASCE 7-02 Minimum Design Loads for Buildings and Other Structures, the 2001 National Design Specification for Wood Construction, and the most recent Allowable Stress Design.

Diagnosing & Repairing House Structure Problems, Edgar O. Seaquist, McGraw Hill, 1980 ISBN 0-07-056013-7 (obsolete, incomplete, missing most diagnosis steps, but very good reading; out of print but used copies are available at Amazon.com, and reprints are available from some inspection tool suppliers). Ed Seaquist was among the first speakers invited to a series of educational conferences organized by D Friedman for ASHI, the American Society of Home Inspectors, where the topic of inspecting the in-service condition of building structures was first addressed.

Defects and Deterioration in Buildings: A Practical Guide to the Science and Technology of Material Failure, Barry Richardson, Spon Press; 2d Ed (2001), ISBN-10: 041925210X, ISBN-13: 978-0419252108. Quoting:A professional reference designed to assist surveyors, engineers, architects and contractors in diagnosing existing problems and avoiding them in new buildings. Fully revised and updated, this edition, in new clearer format, covers developments in building defects, and problems such as sick building syndrome. Well liked for its mixture of theory and practice the new edition will complement Hinks and Cook's student textbook on defects at the practitioner level.

The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, $69.00 U.S., is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume.Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a ten percent discount on any number of copies of the Home Reference Book purchased as a single order. Just enter HRBUS10 in the order payment page "Promo/Redemption" space.

Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: info@carsondunlop.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.

The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors.Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.

TECHNICAL REFERENCE GUIDE to manufacturer's model and serial number information for heating and cooling equipment, useful for determining the age of heating boilers, furnaces, water heaters is provided by Carson Dunlop, Associates, Toronto - Carson Dunlop Weldon & AssociatesSpecial Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.

The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume.

Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.

Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.